1. Field of the Invention
The present invention relates to a compound, a polymer, and a radiation-sensitive composition.
2. Discussion of the Background
In the field of microfabrication represented by production of integrated circuit devices, lithographic technology that enables microfabrication with a line width of 0.10 μm or less has been desired to achieve a higher degree of integration.
A lithographic process has utilized near ultraviolet rays (e.g., i-line). However, it is difficult to implement sub-quarter-micron microfabrication using near ultraviolet rays.
Therefore, use of radiation having a shorter wavelength has been studied to enable microfabrication with a line width of 0.10 μm or less. Examples of such radiation include deep ultraviolet rays (e.g., mercury line spectrum and excimer laser light), X-rays, electron beams, and the like. In particular, technology that utilizes KrF excimer laser light (wavelength: 248 nm) or ArF excimer laser light (wavelength: 193 nm) has attracted attention.
As a resist that is suitable for excimer laser light, various resists (chemically-amplified resists) that utilize a chemical amplification effect due to an acid-dissociable functional group-containing component and a component that generates an acid upon irradiation (exposure) (hereinafter referred to as “acid generator”) have been proposed.
For example, a chemically-amplified resist that includes a resin containing a t-butyl ester group of a carboxylic acid or a t-butyl carbonate group of phenol, and an acid generator has been proposed. This resist utilizes a phenomenon in which the t-butyl ester group or the t-butyl carbonate group contained in the resin dissociates due to an acid generated upon exposure to form an acidic group (e.g., carboxyl group or phenolic hydroxyl group), so that the exposed area of the resist film becomes readily soluble in an alkaline developer.
Such a lithographic process will be required to form a finer pattern (e.g., a resist pattern with a line width of about 90 nm). A pattern having a line width of less than 90 nm may be formed by reducing the wavelength of the light source of the exposure system, or increasing the numerical aperture (NA) of the lens.
However, since a new exposure system is required to reduce the wavelength of the light source, the equipment cost increases. When increasing the numerical aperture (NA) of the lens, since the resolution and the depth of focus have a trade-off relationship, a decrease in depth of focus occurs when increasing the resolution.
In recent years, liquid immersion lithography has been proposed as lithographic technology that can solve the above problems. In liquid immersion lithography, a liquid refractive medium (immersion liquid) (e.g., purified water or fluorine-containing inert liquid) is interposed (at least over the resist film) between the lens and the resist film formed on the substrate during exposure.
According to liquid immersion lithography, the optical space (path) is filled with a liquid (e.g., pure water) having a high refractive index (n) instead of an inert gas (e.g., air or nitrogen) so that the resolution can be increased without causing a decrease in depth of focus in the same manner as in the case of using a short-wavelength light source or a high NA lens. A resist pattern that exhibits excellent resolution and an excellent depth of focus can be inexpensively formed by liquid immersion lithography using a lens provided in an existing system. A polymer, an additive, and the like for forming a resist used for liquid immersion lithography have been proposed (see WO2004/068242, Japanese Patent Application Publication (KOKAI) No. 2005-173474, and Japanese Patent Application Publication (KOKAI) No. 2006-48029, for example).
However, liquid immersion lithography has a problem in that the acid generator and the like are eluted from the resist film when the resist film directly comes in contact with the immersion liquid (e.g., water) during exposure. If the elution volume is large, the lens may be damaged, or the desired pattern shape or sufficient resolution may not be obtained.
When using water as the immersion liquid, if the receding contact angle formed by the resist film and water is low, the immersion liquid may drip from the edge of the wafer during high-speed scanning exposure, or development defects such as watermark defects (i.e., a watermark remains) or blob defects (i.e., the solubility of the resist film decreases due to water permeation so that the pattern locally remains unresolved (i.e., an excellent pattern shape is not obtained)) may occur.
Moreover, the receding contact angle formed by the resist film and water is not necessarily sufficient when using a resist including the resin and the additive disclosed in WO2004/068242, Japanese Patent Application Publication (KOKAI) No. 2005-173474, and Japanese Patent Application Publication (KOKAI) No. 2006-48029. If the receding contact angle is low, the immersion liquid (e.g., water) may drip from the edge of the wafer during high-speed scanning exposure, or development defects such as watermark defects may occur. Furthermore, elution of the acid generator and the like into water is not necessarily sufficiently suppressed.